Conventionally, there have been known many developer supply apparatuses capable of supplying a developer (dry developer or dry toner) to a predetermined object (a photoconductor drum or the like) to which the developer is to be supplied (hereinafter such an object will be referred to as a “target object”) in an image forming apparatus, and many developer electric-field transport apparatuses which are provided in the developer supply apparatuses (see, for example, Japanese Patent Publication (kokoku) No. H5-31146 and Japanese Patent Application Laid-Open (kokai) Nos. 2002-91159, 2003-98826, 2004-333845, and 2005-275127).
Such a developer electric-field transport apparatus is configured to transport a developer in a predetermined developer transport direction by use of a traveling wave electric field. Typically, in the developer electric-field transport apparatus, a large number of elongated electrodes are arrayed on an insulative base material. These electrodes are arranged along the developer transport direction. The developer is stored in a predetermined casing.
In the developer electric-field transport apparatus having the above-described structure, polyphase AC voltages are sequentially applied to the electrodes, whereby a traveling wave electric field is formed. By the action of the traveling wave electric field, the developer in a charged state is transported in the developer transport direction.